Voltage surge arrester

ABSTRACT

A voltage surge or overvoltage arrester comprising at least one response element which becomes conductive upon the occurrence of a voltage surge which exceeds a certain boundary or limit and appears at the connection terminals of the overvoltage arrester, at least one extinguishing element for interrupting the arc supplied by the follower current and at least one arrester resistor connected in series with the extinguishing element and parallel impedances for controlling the voltage distribution. The extinguishing element comprises a switch which can be actuated by an electro-dynamic drive.

United States Patent [191 Amsler et al.

[111 3,851,217 [451 Nov. 26, 1974 VOLTAGE SURGE ARRESTER [75] Inventors: Joachim Amsler, Seon; Walther Otto, Birrwil, both of Switzerland [73] Assignee: Sprecher Schuh AG, Aaru,

Switzerland [22] Filed: Aug. 15, 1973 [21] Appl; No.: 388,640

[30] Foreign Application Priority Data Sept. 8. 1972 Switzerland 13201/72 [52] [1.8. CI 317/16, 317/31, 317/62 [51] Int. Cl. H02h 9/06 [58] Field of Search 317/61.5, 16, 62, 31;

[56] References Cited UNITED STATES PATENTS 2,948,831 8/1960 Stoelting 317/61 X 6/1963 Miller 317/62 X 5/1970 Harder 317/62 X Primary Examiner-James D. Trammell Attorney, Agent, or Firm-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT A voltage surge or overvoltage arrester comprising at least one response element which becomes conductive upon the occurrence of a voltage surge which exceeds a certain boundary or limit and appears at the connection terminals of the overvoltage arrester, at least one extinguishing element for interrupting the arc supplied by the follower current and at least one arrester resistor connected in series with the extinguishing element and parallel impedances for controlling the voltage distribution. The extinguishing element comprises a switch which can be actuated by an electro-dynamic drive.

8 Claims, 5 Drawing Figures PATENTE 5291261974 SHEET 3 OF 4 VOLTAGE SURGE ARRESTER BACKGROUND OF THE INVENTION The present invention relates to anew and improved construction of a voltage surge or overvoltage arrester having at least one response element which becomes conductive upon the occurrence of a voltage surge which exceeds a predetermined boundary or limit and which appears at the connection terminalsof the overvoltage arrester, and further incorporating at least one extinguishing element which interrupts the are supplied by the follower current and at least one arrester resistor connected in series with the extinguishing element as well as having parallel impedances for controlling the voltage distribution.

It is desired for voltage surge or overvoltage arresters, for reasons of coordination of the insulation, to reduce as much as possible the rest voltage based upon the arrester voltage for given arrester currents and also to reduce the response voltages.

The rest voltage can be reduced for a given arrester surge current in that there are selected voltagedependent arrester resistors of large conductivity. However, the follower current at the rated voltage is increased and thus its interruption is rendered more difficult.

Dropping of the response voltages can be attained by appropriately adjusting the normally pre-ionized ignition or firing distance of the response spark gaps or paths. A reduction of the response voltage, however, brings about the disadvantage that there is a smaller ratio of the response voltage to the recurring voltage. Therefore, there is necessary a sufficient re-ignition or re-striking strength of the response spark gap.

In order to fulfill these conditions, it is known to separately arrange the response spark gaps and the extinguishing elements. A prior art arrangement consists of an evacuated housing with a controlled vacuum spark gap serving as the extinguishing element, possessing primary electrodes and a trigger electrode, which is arranged near one of the aforementioned primary electrodes, however located at such a distance therefrom that a trigger spark gap or path is formed. Further, a trigger circuit is provided having a resistance network and a response spark gap system, which is connected electrically in series and parallel to the primary electrodes. The response spark gap system, which normally is not conductive, and which only becomes conductive upon the presence of a predetennined voltage which also appears between the primary electrodes, is arranged in such a way that the resistance network only then is placed into operation when the response spark gap system is conductive. There are provided switching means which serve the purpose of delivering the voltage, which appears at the resistance network when the response spark gaps have responded,'to the controlled spark gap as a firing or ignition pulse.

With this arrangement, the arc should extinguish at the response spark gaps when the vacuum spark gap has ignited. Extinguishing of the arc supplied by the follower current should occur at the vacuum spark gap. Until there appears the recurrent voltage at the response spark gaps there then expires a certain amount of time which is sufficient for restrengthening the cutoff or separation path. In this arrangement, however, the response spark gaps are parallelly connected to the vacuum spark gap which possesses a relatively high voltage drop when the arc burns. Since the voltage is thus not negligibly small at the response spark gap during the duration of ignition of the are at the vacuum spark gap, extinguishing of the are at the ignition spark gaps during the period of burning of the are at the vacuum spark gap is either very difficult or in fact even impossible. The follower current must then be extinguished at the parallelly connected spark gap, at the response spark gaps and at the vacuum spark gap, whereby the vacuum spark gap no longer can be designated as the sole extinguishing element.

It is further disadvantageous with this arrangement that for igniting the controlled vacuum spark gap in the evacuated housing, there must be generated a relatively large amount of metallic vapors, which then renders more difficult extinguishing of the are. A furtherconsiderable drawback of the controlled vacuum spark gap resides in the pronounced wear of the electrodes provided for producing the metallic vapors and having a relatively low melting point. The vapors which emanate from the electrodes possessing a low melting point cannot be condensed in a simple manner and not at a de sired location. The aforementioned drawbacks adversely influence the longevity and operational reliability of the above-discussed overvoltage arrester.

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide an improved construction of overvoltage arrester which is not associated with the aforementioned drawbacks and limitations of the prior art constructions discussed above.

Another and more specific object of the present invention is to provide an improved construction of overvoltage or voltage surge arrester with separately arranged response elements and extinguishing elements, possessing slow responseand rest voltages and positively interrupting the follower current.

Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the invention contemplates that the extinguishing element is a switch which can be actuated by an electro-dynamic drive.

A particularly advantageous arrangement can be realized if the switch and the response elements are connected in series, wherein the switch is closed in the rest state. The electro-dynamic drive, which opens the switch during current flow across the arrester until extinguishing the arc, is connected in series with the response element and the switch. In therest position the movable contact elements are held' in position by at least one spring.

A further advantageous constructional embodiment of the invention resides in the features that the switch is connected parallel to the response element, the switch being opened in the rest state and possessing an arcing or flashover voltage which is above the response voltage of the response element. The electro-dynamic drive which closes the switch during current flow through the arrester is connected in series with the response element.

The switch can be a vacuum switch, a closed gasblast switch with self-blowing characteristics or another suitable switch. the gas-blast switch advantageously can be employed with a sulphur hexafluoride (SP extinguishing gas.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 is a circuit diagram of an overvoltage arrester with a vacuum switch as the extinguishing element connected in series with the response spark path;

FIG. 2 is a circuit diagram of an overvoltage arrester with a vacuum switch as the extinguishing element connected in parallel with the response spark path;

FIG. 3 is a circuit diagram of a further embodiment of overvoltage arrester with parallel connected responseand extinguishing elements, with response spark path and gas-blast switch;

FIG. 4 illustrates in cross-sectional view a portion of an overvoltage arrester with series connected response spark paths and extinguishing elements; and

FIG. 5 is a portion of an overvoltage arrester with parallel connected response spark paths and extinguishing elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, in FIG. 1 there is illustrated a schematic circuit diagram of an overvoltage arrester or voltage surge arrester, generally indicated by reference character V. This arrester is connected by means of its connection terminals between the conductor 1 and ground 2. Upon the occurrence of a voltage surge or overvoltage at the conductor 1 the response element 3 of the arrester V responds, this response element consisting of a pre-ionized spark path or gap 3a. The arrester surge current then flows via the closed vacuum switch 4, the auxiliary spark path or gap 5 which has responded and the resistor 6 to the arrester resistor arrangement 7, 8 and to ground 2. The arrester resistor arrangement 7, 8 consists of the parallel circuit connection of the linear resistor 7 primarily provided for the follower current and the voltagedependent resistor 8 intended for arresting or dissipating the surge current.

As soon as the arrester surge current has decayed, the auxiliary spark gap or path 5 extinguishes because it is connected in parallel with the excitation coil 9 of the electro-dynamic drive D of the vacuum switch 4, this excitation coil possessing a relatively small impedance for the network frequency follower current. The electro-dynamic drive D consists of an electromagnet with a head or pot-shaped core 10 and an armature 11. Traction or tension springs 12 retain the vacuum switch 4 closed in the rest position. When the follower current, after extinguishing of the auxiliary spark gap or path 5, flows via the excitation coil 9, then the armature 1 l which is force-lockingly or positively connected with the movable contact element or piece 13 of the vacuum switch 4, is pulled against the spring force towards the pot-shaped core 10 and the vacuum switch 4 is opened. This vacuum switch 4 is opened for such time until the arc is extinguished and the follower current is interrupted. When the follower current is inter rupted the tension springs 12 again close the vacuum switch 4. The voltage distribution across the preionized spark gap or path 3, the vacuum switch 4 and the electro-dynamic drive D is ensured for by the control resistors l4, l5 and 16. For greater voltages a number of the units depicted in FIG. 1 are then connected in series.

According to the schematic circuit diagram depicted in FIG. 2, the response element 3 and the vacuum switch 4 are connected in parallel. In this case the vacuum switch 4 remains open in the rest position. Upon the occurrence of an overvoltage at the conductor 1 the response element 3 responds, this response element consisting of the pre-ionized spark gap or path 3a. The arresting current surge flows via the auxiliary spark gap or path 5, which has responded, to the arrester resistors 7 and 8 and then to ground 2. After decay of the arrester surge current the spark path or gap 5 again extinguishes and the follower current is conducted via the excitation coil 17 of the E-core 18 connected with the vacuum switch 4. The armature 19 which is forcelockingly or positively connected with the movable contact element 13 of the vacuum switch 4 is attracted against the force of the pressure of the compression springs 20 and the vacuum switch 4 is closed. At this moment the spark path or gap 3 extinguishes and interrupts the follower current by means of the excitation coil 17 of the electro-dynamic drive of the vacuum switch 4. Now the vacuum switch 4 again opens under the action of the springs 20 and the arc which prevails in the vacuum switch 4 is extinguished during the next null cross-over of the network-frequency follower current. During extinguishing of the follower current in the vacuum switch 4 the insulation of the response element 3 can again build-up, so that upon occurrence of the recurring voltage there is not to be expected any reignition. The potential control of the arrester occurs with the aid of the control resistors 14 and 21.

In FIG. 3 there is again schematically illustrated a further exemplary embodiment of the overvoltage arrester depicted schematically in FIG. 2. The response element 3 in this arrangement again consists of a spark path or gap 3a. The switch 23 is a gas-blast switch with a self-blowing action and is filled with for instance sulphur hexafluoride (SF as the extinguishing gas. Upon the occurrence of an overvoltage at the conductor 1 the spark gap or path 3a and the auxiliary spark path 24 respond and the arrester surge current flows to the arrester resistors 7, 8 and to ground 2. As soon as the arrester surge current has sufficiently decayed then the auxiliary spark path 24 extinguishes, and the follower current is delivered to the excitation coil 25 of the electro-dynamic drive D of the switch 23. The movable switching pin 26 of the gas-blast switch 23 is retained in the rest position in an intermediate position by the springs 27 and 28. The follower current, which flows through the excitation coil 25, brings about that the armature 29 which is force-lockingly or positively connected with the switching pin 26 will be moved upwardly towards the E-core 30 of the drive, so that the switch 23 closes. When the switch 23 is closed the follower current commutates from the spark gap or path 3 to the switch 23. Now the excitation coil 25 is without current. At this point the follower current flows to the switch 23 via the excitation coil 31 of the lower E-core 32, whereby the switch-off movement of theswitch 23 is accelerated. After the follower current in the switch 23 is interrupted the armature 29 returns back into its rest position.

The overvoltage arrester which has been partially shown in sectional view in FIG. 4 is accommodated in a housing 33 formed of a suitable insulating material. The housing 33 is closed at the top and bottom by suitable and therefore not particularly illustrated caps which carry the connection terminals. In FIG. 4 there has only been shown a part of the overvoltage arrester consisting of a number of similar constructed units which are arranged in stack formation in the common housing 33. The construction of the units extensively corresponds to the schematic circuit diagram of FIG. 1. The units consist of the pre-ionized spark paths 3a of the response elements 3 which are connected in parallel with the control resistors 14, the vacuum switch 4 with the electro-dynamic drive D, the auxiliary spark gap or path 5, the linear arrester resistor 7, the voltagedependent arrester resistor 8 and the control resistors and 16. The movable contact or contact element 13 of the vacuum switch 4 is force-lockingly connected with the armature 11 consisting of a ferro-magnetic material. The pot-shaped core 10 carries the excitation coil 9 and the compression springs 34 providing the requisite contact pressure for the vacuum switch 4. The auxiliary spark gap or path 5 is formed between the floor of the pot core 10 and the ring-shaped raised portion 36 formed at the intermediate plate 35.

After response of the response spark gaps or paths 3a and after extinguishing the auxiliary spark gap or path 5 the follower current flows via the excitation coil 9. The armature 11 is attracted towards the pot-shaped core 10, whereby the check valve 37 is opened and the gas can flow out of the smaller size space between the armature l1 and the pot-shaped core 10. When the follower current becomes null then the armature 11 is pushed-up by the compression spring 34 and the vacuum switch 4 is closed. In order to be able to hold the vacuum switch 4 open during the null crossover of the follower current and to delay closing of the switch after an arc has been extinguished, the return flow of the gas in the space between the armature 11 and the potshaped core 10 is slowed down. The gas can only flow back in this space through the small hole or bore 38, so that there is realized the desired delay of the closing movement of the vacuum switch 4.

The elements which can be stacked upon one another of the overvoltage arrester depicted in FIG. 5 consist of the pre-ionized response spark paths 3a of the response elements which are connected parallel to the control resistors 14, the vacuum switches 4 with the electro-magnetic drives D and each of which vacuum switch is arranged concentric to the response spark paths, the auxiliary spark path 24, the control resistor 15, the linear arrester resistor 7 and the voltagedependent arrester resistor 8. The movable contact element 13 of the vacuum switch 4 is force-lockingly connected with two armatures 39 and 40 of two E-magnets 41 and 42 of the associated electro-dynamic drive D. Upon response of the spark paths or gaps 3a the auxiliary spark path 24 also ignites, so that the arrester surge current can be conducted to the arrester resistors 7 and 8. After decay of the arrester surge current the auxiliary spark path extinguishes and the follower current flows through the excitation winding or coil 43. The E- magnet attracts the armature 40 and thus switches-in the vacuum switch. The are extinguishes at the spark paths 3a because it has become short-circuited by the vacuum switch. Now the follower current flows via the excitation core 44, with the result that the E-magnetic 41 attracts the armature 39 and the vacuum switch 4 is switched-off. After extinguishing of the arc in the vacuum switch 4 the movable contact element 13 of such vacuum switch 4 returns back into the rest position detemiined by the resilient closure membrane or diaphragm 45 of the vacuum switch 4. The intermediate elements 46 and 47 which are formed of metal surround the electro-dynamic drive and screen such against foreign electro-magnetic fields. The stacked elements are housed in a cylinder 48 formed of a suitable insulating material.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, by may be otherwise variously embodied and practiced within the scope of the following claims.

Accordingly, what is claimed is:

1. An overvoltage arrester comprising at least one response element which becomes conductive upon occurrence of an overvoltage which exceeds a certain boundary value, said overvoltage appearing at connection terminals of the overvoltage arrester, at least one extinguishing element for interrupting an arc supplied by the follower current, at least one arrester resistor connected in series with the extinguishing element, parallel impedances for controlling the voltage distribution, said extinguishing element comprising a switch, and an electro-dynamic drive for actuating said switch, said switch being connected in parallel with the response element, the switch in its rest state being opened and possessing a flashover voltage which is above the response voltage of the response element.

2. The overvoltage arrester as defined in claim 1, wherein the electro-dynamic drive closes the switch during current flow through the arrester, said electrodynamic drive being connected in series with the response element.

3. The overvoltage arrester as defined in claim 1, wherein the switch is opened in its rest state in an intermediate position, said electro-dynamic drive closing the switch upon occurrence of an overvoltage, said electro-dynamic drive being connected in series with the response element, and a drive which subsequently opens the switch connected in series with said switch.

4. The overvoltage arrester as defined in claim 1, wherein said switch has a movable contact element displaceable into said rest position, and at least one spring for retaining the contact element in its rest position.

5. The overvoltage arrester as defined in claim 1, wherein the electro-dynamic drive is provided with at least one coil, and said at least one coil of the electrodynamic drive is bridged by an auxiliary spark gap.

6. The overvoltage arrester as defined in claim 1, wherein the switch is a vacuum switch.

7. The overvoltage arrester as defined in claim 1, wherein the switch is an enclosed gas-blast switch.

8. The overvoltage arrester as defined in claim 1, wherein the response element comprises a pre-ionized spark gap. 

1. An overvoltage arrester comprising at least one response element which becomes conductive upon occurrence of an overvoltage which exceeds a certain boundary value, said overvoltage appearing at connection terminals of the overvoltage arrester, at least one extinguishing element for interrupting an arc supplied by the follower current, at least one arrester resistor connected in series with the extinguishing element, parallel impedances for controlling the voltage distribution, said extinguishing element comprising a switch, and an electrodynamic drive for actuating said switch, said switch being connected in parallel with the response element, the switch in its rest state being opened and possessing a flashover voltage which is above the response voltage of the response element.
 2. The overvoltage arrester as defined in claim 1, wherein the electro-dynAmic drive closes the switch during current flow through the arrester, said electro-dynamic drive being connected in series with the response element.
 3. The overvoltage arrester as defined in claim 1, wherein the switch is opened in its rest state in an intermediate position, said electro-dynamic drive closing the switch upon occurrence of an overvoltage, said electro-dynamic drive being connected in series with the response element, and a drive which subsequently opens the switch connected in series with said switch.
 4. The overvoltage arrester as defined in claim 1, wherein said switch has a movable contact element displaceable into said rest position, and at least one spring for retaining the contact element in its rest position.
 5. The overvoltage arrester as defined in claim 1, wherein the electro-dynamic drive is provided with at least one coil, and said at least one coil of the electro-dynamic drive is bridged by an auxiliary spark gap.
 6. The overvoltage arrester as defined in claim 1, wherein the switch is a vacuum switch.
 7. The overvoltage arrester as defined in claim 1, wherein the switch is an enclosed gas-blast switch.
 8. The overvoltage arrester as defined in claim 1, wherein the response element comprises a pre-ionized spark gap. 